Usako

I look at the Roose thing as Ned following the adage of "keep your friends close and your enemies closer". He didn't trust the man, but he had given him no reason to act against him, par Roose's own philosophy of "a peaceful land, a quiet people." So because of that, it is better to keep him close, keep him in his counsel, in respect of the position and power of the Boltons. And, yes we're told later through Jon that Ned had warned him not to trust him, which would mean Robb had been told that as well, but would have also been told that there was no point in antagonizing the Boltons without Roose giving reason. Would he have told this to Cat? Unlikely. So, she would just see the "public" image of Roose coupled with his past interactions with Ned. I'm not a fan of Cat at all, but without the benefit of hindsight, I can see based on that why she would have pushed for making Roose in charge. Yes, it might have been better to appoint the Greatjon and keep Roose close to Robb, but that's a total unknown. We don't know enough about that scenario as opposed to what we were giving to really answer that. Only George would know that.